Ideologies! Why isn't this on the list?
Having a cold-war progression in the late game puts hairs on my chest.
I debated putting ideologies on the list.
On the one hand, they were overhauled from G&K (G&K technically had diplo hits already based on Order, Freedom, and Autocracy) in a noticeable enough way to warrant possible inclusion on the list. They now also produce unhappiness and can cause city flipping, which are interesting changes.
On the other hand, the changes to ideology are really just three tweaks, two of which are somewhat minor:
1) a couple of policies were added per ideology
2) unhappiness was added
while the third is more major
3) city-flipping depending on pressure and extreme unhappiness
Compared to the other additions, I thought ideologies were fairly minor. The SP trees are also fairly minor changes, given that most of the changes were just moving around existing policies and dividing them up better according to purpose.
That said, I could have made the list longer I guess, but these just seemed like the most major additions to the game. But I understand the point you make.